The present application is based on and claims priority from Japanese Patent Application 2000-113967, filed Apr. 14, 2000, the contents of which are incorporated herein by reference.
1. Field of the Invention
The invention relates to a vehicle AC generator that is driven by an engine of a vehicle, such as a passenger car or a truck.
2. Description of the Related Art
In these days, the engine compartment of vehicles has become narrower as vehicles have adopted slant nose styles in order to reduce vehicle""s running resistance and, also, to satisfy demands for wider passenger compartment. Accordingly, the space in the engine compartment for mounting an AC generator has become narrower.
Rotation speed of vehicle AC generators has been lowered because engine speed is lowered to improve fuel consumption of vehicles. On the other hand, the output power of AC generators has increased in order to satisfy the demand for increasing electric power to be supplied to various electric devices such as safety control devices. Thus, the demand for small, powerful and inexpensive vehicle AC generators have been increased.
The output power of an AC generator can be increased if winding resistance of a rotor is reduced. However, if the winding resistance is reduced, field current to be controlled by an IC regulator increases, resulting in temperature rise of the IC regulator. This necessitates more cooling of the IC regulator within a limited space in order to ensure the reliability of the IC regulator.
U.S. Pat. No. 6,060,802 or its corresponding Japanese Application, JP-A-11-164518, discloses an IC regulator that is disposed between a brush holder and a connector. An axial cooling air passage is formed along a heatsink of the IC regulator to cool the IC regulator.
Because the IC regulator of the above prior art is disposed opposite the brush holder, heat generated by electric current flowing in the brushes and by friction between the brushes and slip rings is transmitted to the brush holder. As a result, the heat is radiated from the brush holder to the IC regulator. The IC regulator also has a surface that directly faces the heat sink of the voltage regulator from which heat radiates.
Under a certain circumstance, temperature of the brush holder and the cooling fins of the rectifier may rise by 100xc2x0 C. or more, and temperature of the IC regulator may rise by 60xc2x0 C., although the temperature rise of the IC regulator by itself is 30xc2x0 C.
It is possible to reduce such temperature rise caused by the heat radiation if the IC regulator is disposed remote from the brush holder and the rectifier""s cooling fin. However, the rear portion of the AC generator becomes too large to be mounted in a limited space of a vehicle.
Therefore, a main object of the invention is to provide a vehicle AC generator in which an IC regulator is effectively cooled without increasing the size of the AC generator or sacrificing cooling performance of other parts with the IC regulator being disposed in a limited space.
According to a main feature of the invention, an AC generator for a vehicle includes a rotor having a field coil, a stator having an armature coil, a frame for supporting the rotor and stator, a rear cover having an air intake window, a pair of cooling fins having a common cutout section thereby forming an accommodation space between the frame and the rear cover, a plurality of positive and negative rectifier elements respectively fixed to the pair of cooling fins, a brush-holder disposed in the accommodation space to hold a pair of brushes, a connector case disposed in the accommodation space radially outside the brush holder so as to form a cooling air passage connecting the air intake passage around the connector case and an IC regulator disposed in the cooling air passage around the connector case to face the rear cover. In addition, the IC regulator has a heatsink disposed opposite the air intake window of the rear cover.
Therefore, direct heat radiation from the cooling fins and the brush holder is interrupted by the connector case, thereby controlling temperature rise of the IC regulator.
The heatsink of the IC regulator may be disposed at a radially outside portion of the connector case.